Ash's father is the unnamed father of Ash Ketchum from the Pokémon Anime series and husband to Delia Ketchum. Ash's dad is Mr. Mime due to interspecies relations Ash's dad had a horrible accident which turned him into Mr. Mime.
From very minor portions of dialogue, it can be assumed that his father started on a journey from Pallet Town much like Ash. Never formally introduced, the identity of his father has always been under heavy speculation. This speculated character however, have attained no hard evidence that they are in fact related to Ash in any way. In addition to that, during an interview with a storyboard artist for the Anime series, the artist stated that Ash's father is a man who is on his own Pokémon journey as a Trainer. Rumors say that Silver from the Pokémon Chronicles could be his father. In The Spell of the Unown the commentary version, the producer announced that more about him will be revealed in season 5, which eventually turned out to be untrue.